Modular Programming with Functions

1
Modular Programming with Functions

• B. Ramamurthy
• Chapter 5

2
Introduction

• Complex problems Divide and conquer
• Reusability of code
• Modular design of software to enhance readability
  and maintenance.
• Abstraction
• Information hiding

3
Structure Charts

• Structure charts are often used to represent the
  modular design.
• Here is an example of a structure chart for
  StickFigure.

main
drawTriangle
drawHollowRectangle
drawRectangle
4
Libraries of Functions

• We have used functions from many libraries
• cmath pow, sin, cos
• fstream open, close, get, set
• iomanip setw, setprecision
• iostream ltlt , gtgt
• Programmers can define functions for use in their
  program programmer-defined functions.

5
Functions Definition

• Function header
• Function parameters
• Function body
• Function return value
• In fact
• int main()
• return 0
• is a function.

6
Example StickFigure


























7
Part of Stick Figure
















Step1 Draw triangle Step2 Draw
rectangle Step3 Draw hollow rectangle
8
drawTriangle(..)
for (int i3 0 i3 lt row i3) for (int k
1 klt offset k)
coutltlt ' ' for (int j 1 j
lt col j ) cout ltlt'' offset offset
-1 col col 2 coutltlt endl
9
drawRectangle(..)
for (int i4 1 i4 lt length i4) for
(int k 1 klt offset k)
coutltlt ' ' for
(int j 1 jlt width j) cout
ltlt'' coutltlt endl
10
drawHollowRectangle(..)
for (int i4 1 i4 lt length i4) for
(int k 1 klt offset k) coutltlt ' ' if
((i4 1 ) (i4 length)) for (int j 1
jlt width j) cout ltlt'' else c
out ltlt '' for (int k 1 klt width-2
k) cout ltlt ' cout ltlt
'' coutltlt endl
11
Function syntax

• type functioName (parameters)
• declare local variables/constants
• statements

12
Example

• int factorial (int n)
• int prod
• for (int i 1 i lt n i)
• prod prod i
• return prod